CNC Machining of Invar 36 (Low-Expansion Alloy)
Invar 36 barely grows when it gets warm - roughly one fifth of the expansion of steel. For optical benches, laser cavities and metrology frames that stability is the whole point, and it has to survive machining.
Why it is hard to machine
Low expansion comes with awkward machining habits: Invar is gummy, work-hardens readily and conducts heat poorly, so it tears, burrs and moves if the process is not controlled. Its value is dimensional, so any stress left in the part defeats the reason it was specified.
Process controls that matter
Work hardening and tearing
Invar is gummy and hardens quickly. Sharp geometry, constant feed and generous chip clearance keep the cut clean.
Heat and dimensional movement
Poor conductivity traps heat, and thermal growth is exactly what Invar is meant to avoid. Light cuts and controlled finishing keep it stable.
Residual stress
Stress left in the part shows up later as drift. Staged machining and stress-aware fixturing protect the low-expansion benefit.
Tolerances, inspection and documentation
Typical applications
Optical benches and mounts, laser and photonics hardware, metrology frames, satellite and precision-instrument components.